Hybrid beamforming for Terahertz (THz) ultra-massive multiple-input multiple-output (UM-MIMO) systems is a promising technology for 6G space-air-ground integrated networks, which can overcome huge propagation loss and offer unprecedented data rates. With ultra-wide bandwidth and ultra-large-scale antennas array in THz band, the beam squint becomes one of the critical problems which could reduce the array gain and degrade the data rate substantially. However, the traditional phase-shifters-based hybrid beamforming architectures cannot tackle this issue due to the frequency-flat property of the phase shifters. In this paper, to combat the beam squint while keeping high energy efficiency, a novel dynamic-subarray with fixed true-time-delay (DS-FTTD) architecture is proposed. Compared to the existing studies which use the complicated adjustable TTDs, the DS-FTTD architecture has lower power consumption and hardware complexity, thanks to the low-cost FTTDs. Furthermore, a low-complexity row-decomposition (RD) algorithm is proposed to design hybrid beamforming matrices for the DS-FTTD architecture. Extensive simulation results show that, by using the RD algorithm, the DS-FTTD architecture achieves near-optimal array gain and significantly higher energy efficiency than the existing architectures. Moreover, the spectral efficiency of DS-FTTD architecture with the RD algorithm is robust to the imperfect channel state information.
翻译:Terahertz (Thz) 超超超缩成型多输入多输出(UM-MIMO) 系统是6G空间-空地综合网络的一个很有希望的技术,可以克服巨大的传播损失,提供前所未有的数据率。Thz波段超大带宽和超大天天线阵列,梁斜形成为可以降低阵列增量和大幅降低数据率的关键问题之一。然而,传统的基于分阶段更替者的混合组合成型结构由于阶段变换器的频率膨胀属性而无法解决这一问题。在本文件中,为了在保持高能效的同时打击波纹光亮,提出了一种具有固定真实时间delay (DS-FTTD) 架构的新动态次阵列。与使用复杂可调整的 TTDs,DS-FTD结构的电力消耗和硬件复杂性较低,而且由于成本低的FTTD转换成本, 低的相偏缩行偏缩式变速变速配置(RDD) 近端变压阵列(RD) 阵列(RD-FT) 矩阵结构结构将大大地显示D-RD-RD-ralmaislation 结构的Mex-ral-ral-ralmax